A compound from rooibos tea called isoorientin didn’t protect insulin-producing cells in lab-grown rat cells when those cells were stressed out by harmful chemicals — and it didn’t change any of the key genes that help cells fight stress or avoid dying, so it probably doesn’t help protect these cells at all.

When sugar-producing cells in rats are under stress, a green tea-like drink from rooibos plants helps them survive by turning down genes that cause cell death—without turning on the body’s usual antioxidant defense system.

When scientists stressed rat pancreatic cells with harmful chemicals, adding a green tea-like extract from rooibos or one of its natural compounds helped the cells survive much better—up to nearly 70% more than stressed cells without it.

When sugar-producing cells in rats are under stress from harmful molecules, two natural compounds called aspalathin and 3-hydroxyphloretin help the cells fight back by turning on their internal defense genes and turning off a gene that makes stress worse.

In lab-grown rat pancreatic cells under stress, a natural compound called 3-hydroxyphloretin at a tiny dose (5 micromolars) helped the cells survive better—up to double in some cases—but if you give it more, it starts killing the cells instead, so the safe dose is very narrow.